Tuning of the Cloud Point of Promethazine Hydrochloride with Surfactants and Polymers

The effect of additives (surfactants and polymers) and pH on the clouding behavior of promethazine hydrochloride (PMT, a phenothiazine drug) was investigated. Cloud point (CP) decreases with increase in pH due to deprotonation of drug molecules. The same trend occurs in the presence of surfactants. However, at constant pH, and depending on their structure and nature, these additives behave differently. Anionic surfactants show peaked behavior, whereas cationic (conventional as well as geminis) and non-ionic surfactants increase the CP, although the mechanisms differ. Cationic surfactants hinder drug association (due to interaggregate repulsion) resulting in an increase in CP, while non-ionic surfactants form mixed micelles with the drug, increasing micelle hydration and CP. Polymers can cause both a decrease as well as an increase in CP, depending on their molecular weight. A large CP increase (with the increase in surfactant concentration) for gemini surfactants suggests they are excellent candidates for drug delivery.

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Investigation of Tool Wear and Surface Finish by Analyzing Vibration Signals in Turning Assab-705 Steel

Various occurrences in machining influence the machining dynamics and thus produce vibration in the cutting tool-workpiece arrangement. In this investigation, with tri-axial accelerometer mounted on the tool-holder in turning ASSAB-705 steel, vibration signals have been captured with and without cutting. The nature of vibrations arising in the cutting tool at different cutting conditions has been investigated. It has been observed that the RMS amplitude of vibration along all three axes for the increasing cutting speed was mixed in nature; however, an increasing trend was noticed in the vibrations along the feed, V_x and radial, V_y directions. The vibration along the main cutting direction, V_z was mixed, initiated by large vibration and then decreased until a particular cutting speed was reached and finally increased steadily. The feed vibration component, V_x has a similar response to the change of the workpiece surface roughness, while the other two components, V_y and V_z have the more coherent response to the rate of flank wear progression throughout the tool life. The natural frequency of different machine parts vibration has been found to be within the band of 0 Hz – 4.2 kHz, whereas the frequencies of different occurrences in turning varied between 98 Hz and 42 kHz.     

Biomimetic Approach for the Production of 3D Woven Spherical Composite Applied in Apparel Protection and Performance

Applied Composite Materials - Current sports bras are typically manufactured via a cut and sew process resulting in a high volume of post-production material waste. Seams derived from this cut and...     

Applying gray-scaled detour phase hologram on liquid crystal on silicon spatial light modulator (LCoS-SLM)

In order to solve the representation problem of computer-generated holograms, multiple algorithms have been devised. One of which is the well-known detour phase method. This method has recently been modified to be optimized to display the generated hologram on twisted nematic spatial light modulators. In this paper, we apply the modified gray-scaled detour phase holograms on another type of spatial light modulators, which is of utmost importance in the field, namely the reflective liquid crystal on silicon spatial light modulator.     

A new approach to investigate tool condition using dummy tool holder and sensor setup

The industrial demand for automated machining systems to enhance process productivity and quality in machining aerospace components requires investigation of tool condition monitoring. The formation of chip and its removal have a remarkable effect on the state of the cutting tool during turning. This work presents a new technique using acoustic emission (AE) to monitor the tool condition by separating the chip formation frequencies from the rest of the signal which comes mostly from tool wear and plastic deformation of the work material. A dummy tool holder and sensor setup have been designed and integrated with the conventional tool holder system to capture the time-domain chip formation signals independently during turning. Several dry turning tests have been conducted at the speed ranging from 120 to 180?m/min, feed rate from 0.20 to 0.50?mm/rev, and depth of cut from 1 to 1.5?mm. The tool insert used was TiN-coated carbide while the work material was high-carbon steel. The signals from the dummy setup clearly differ from the AE signals of the conventional setup. It has been observed that time-domain signal and corresponding frequency response can predict the tool conditions. The rate of tool wear was found to decrease with chip breakage even at higher feed rate. The tool wear and plastic deformation were viewed to decrease with the increased radius of chip curvature and thinner chip thickness even at the highest cutting speed, and these have been verified by measuring tool wear. The chip formation frequency has been found to be within 97.7 to 640?kHz.     

基于自钻式旁压仪的残积土原位力学特性试验研究

残积土属区域性特殊土,准确获得其力学性质指标是各类工程场地地基处治及承载力评价的必要条件。针对典型花岗岩残积土层,在20 m深度范围内开展自钻式旁压试验,获得表征土体原始水平应力、强度与刚度的相关指标,类比分析深度与水平方向土体力学性质的差异性,并论证了土体刚度在不同应变水平下的衰减规律。结果表明,该场地浅层土体刚强度指标差异性较大,存在明显的风化壳,导致剪切模量及变形参数沿深度呈先减小后增大的趋势;土体割线剪切模量Gs,切线剪切模量Gt随剪应变变化关系具有明显的非线性特性,在小应变范围(γc≤0.3%)内Gs,Gt快速衰减,在γc=2.0%~3.0%时,趋于平稳,采用非线性分析方法得到的模量值较为合理,认为在该类场地工程设计中,剪切模量的选取宜基于自钻式旁压试验结果,根据不同应变水平确定,采用线性割线法得到的剪切模量Gur偏于冒险。同时发现,小应变时剪切模量值相对于土体差异较为敏感,为准确获得土性参数,可适当增加浅层土体测试数量。     

Genotypic diversity of stress response in Lactobacillus plantarum, Lactobacillus paraplantarum and Lactobacillus pentosus

Lactobacillus plantarum, Lactobacillus pentosus and Lactobacillus paraplantarum are three closely related species which are widespread in food and non-food environments, and are important as starter bacteria or probiotics. In order to evaluate the phenotypic diversity of stress tolerance in the L. plantarum group and the ability to mount an adaptive heat shock response, the survival of exponential and stationary phase and of heat adapted exponential phase cells of six L. plantarum subsp. plantarum, one L. plantarum subsp. argentoratensis, one L. pentosus and two L. paraplantarum strains selected in a previous work upon exposure to oxidative, heat, detergent, starvation and acid stresses was compared to that of the L. plantarum WCFS1 strain. Furthermore, to evaluate the genotypic diversity in stress response genes, ten genes (encoding for chaperones DnaK, GroES and GroEL, regulators CtsR, HrcA and CcpA, ATPases/proteases ClpL, ClpP, ClpX and protease FtsH) were amplified using primers derived from the WCFS1 genome sequence and submitted to restriction with one or two endonucleases. The results were compared by univariate and multivariate statistical methods. In addition, the amplicons for hrcA and ctsR were sequenced and compared by multiple sequence alignment and polymorphism analysis. Although there was evidence of a generalized stress response in the stationary phase, with increase of oxidative, heat, and, to a lesser extent, starvation stress tolerance, and for adaptive heat stress response, with increased tolerance to heat, acid and detergent, different growth phases and adaptation patterns were found. Principal component analysis showed that while heat, acid and detergent stresses respond similarly to growth phase and adaptation, tolerance to oxidative and starvation stresses implies completely unrelated mechanisms. A dendrogram obtained using the data from multilocus restriction typing (MLRT) of stress response genes clearly separated two groups of L. plantarum strains from the other species but there was no correlation between genotypic grouping and grouping obtained on the basis of the stress response pattern, nor with the phylograms obtained from hrcA and ctsR sequences. Differences in sequence in L. plantarum strains were mostly due to single nucleotide polymorphisms with a high frequency of synonymous nucleotide changes and, while hrcA was characterized by an excess of low frequency polymorphism, very low diversity was found in ctsR sequences. Sequence alignment of hrcA allowed a correct discrimination of the strains at the species level, thus confirming the relevance of stress response genes for taxonomy.     

Thixotropic mechanism of clay: A microstructural investigation

Clays with high sensitivity exhibit varied degrees of thixotropic characteristics. Previous research has been focused on dilute suspensions, but only a few studies have investigated normal clay with water contents lower than the liquid limit. Given the limited studies performed, the thixotropic behavior of clays and the underlying mechanism remain ambiguous, particularly in the microscopic scale. In this study, samples of Zhanjiang clay from southern China were used to elucidate the thixotropic process. The samples were agitated and then subjected to unconfined compressive strength and pocket penetrometer tests, scanning electron microscopy, and mercury intrusion porosimetry to evaluate their regain strength and microstructure. After 500 d of thixotropy, the strength of the Zhanjiang clay was 2.58 times higher than that after the disturbance and significantly higher than that of the other clays reported in the literature. These findings provide evidence that thixotropy is a process in which the dispersed structure is transformed into a flocculent structure through the homogenization of the pore size distribution caused by particle movement. This phenomenon may be due to the changes in the interaction of attractive and repulsive forces between particles. Given the experimental findings, a thixotropic mechanism for clay is proposed. This study will be beneficial for predicting the strength of disturbed soils.     

Mixed Micellization of Cationic Gemini Surfactants with Primary Linear Alkylamines

Due to the potential use of amines as co-surfactants in microemulsions, the effect of adding alkylamines (C₄–C₈NH₂) on the aggregation properties of cationic gemini surfactants [pentanediyl-1, 5-bis(dimethylcetylammonium bromide) and hexanediyl-1, 6-bis(dimethylcetylammonium bromide), referred to as 16-5-16 and 16-6-16 compounds] has been studied using tensiometry at 303 K. Data on critical micelle concentration (CMC), the surface properties C₂₀ (the surfactant concentration required to reduce the surface tension by 20 mN/m), Г_max (maximum surface excess), A _min (minimum surface area per molecule) evaluated from the surface tension versus surfactant concentration plot, the interaction parameters β^σ (for mixed monolayer formation at the aqueous solution/air interface), and β^m (for mixed micelle formation in aqueous medium) are reported. A synergistic interaction was observed both in the micelle as well as at interface, as evident from interaction parameters. Theoretical models of Clint, Rubingh and Rosen were used to explain and compare the results. More synergistic interaction was observed in 16-5-16 as compared to 16-6-16. The CMC values of 16-s-16 (s = 5, 6) decreased with increasing amine concentrations and the extent of the effect followed the sequence: octylamine > heptylamine > hexylamine > pentylamine > butylamine.     

Threshold Power of Canonical Antennas for Inducing SAR at Compliance Limits in the 300–3000 MHz Frequency Range

A study of the specific absorption rate (SAR) in an exposed body induced by canonical antennas is presented, with the aim of determining an upper bound for the antenna transmit power that demonstrates that a product is inherently compliant with internationally accepted radio frequency (RF) exposure limits. Starting from the fundamental limits in antenna quality factor (Q) and the corresponding bandwidth, several antenna sizes are selected, and their SAR distributions are computed using the method of moments (MoM) and finite-difference time domain (FDTD) method in the frequency range 300-3000 MHz. The threshold powers are then determined, below which the peak 1-g and 10-g averaged SAR would not exceed the limits specified in international exposure standards. From the data, simple expressions are derived to estimate the threshold power over a wide range of antenna sizes, frequencies, and distances from the body. It is demonstrated that the results presented in this paper are conservative in comparison with the measured SAR data of real products as well as other published data